An adjustment fitting of the type mentioned at the beginning is used in particular for adjusting the backrest of a vehicle seat. For this purpose, for example, the first fitting part is connected to the backrest and the second fitting part is connected to the seat surface of the vehicle seat. The use of a wobble mechanism has been tried and tested here, since it constitutes a rotary connection which manages with comparatively few elements and at the same time comprises a gear mechanism.
Such an adjustment fitting which is described at the beginning is known, for example, from DE 29 21 588 A1. In this case, the wobble mechanism comprises a central wheel which is rotatable about a central axis, and a revolving wheel which is arranged in the interior of the central wheel eccentrically with respect to the central axis. The central wheel and the revolving wheel here form, with respect to each other, an eccentric receiving space in which a first eccentric and a second eccentric are arranged rotatably in relation to each other, as a result of which a variable eccentricity is formed. In order to actuate the wobble mechanism, a driver disk which is rotatable by means of an adjustment spindle is provided as the transmission element. The driver disk has cutouts which are in engagement with driver pins arranged on the eccentrics. Furthermore, a mechanically acting coupling element (spring) is provided which, in the inoperative state of the adjustment fitting, rotates the eccentrics in relation to each other in such a manner that their overall eccentricity is increased. By this means, the revolving wheel is brought into a position in which it engages in a play-free manner in the central wheel. When the driver disk is rotated, an eccentric is rotated in each case via the driver pin, thus reducing the overall eccentricity. By this means, the revolving wheel is brought into a position in which it engages with play in the central wheel. The revolving wheel can be rotated in relation to the central wheel via the driver disk in a manner such that it wobbles with revolving eccentricity. By this means, the first fitting part rotates relative to the second fitting part with a corresponding transmission ratio which is determined by the ratio of the number of teeth of the external toothing of the revolving wheel to the number of teeth of the internal toothing of the central wheel.
The adjustment fitting known from DE 29 21 588 A1 is free from play in its inoperative position, as a result of which rattling is avoided. However, this adjustment fitting is disadvantageously relatively stiff and has an actuating asymmetry with respect to the direction of rotation.
Further adjustment fittings which have a wobble mechanism and in which the revolving wheel rests in a play-free manner on the central wheel in an inoperative position are known from DE 195 27 374 C2 and DE 103 28 300 A1.